Fix create transaction locking issue (#13)

* define default attributes model

* Revert "define default attributes model"

This reverts commit e99c9d8.

* fix transcation lock issue

Co-authored-by: Caleb Xiang <[email protected]>

Author: calebx

nested_set.go

@@ -167,8 +167,7 @@ func Create(db *gorm.DB, source, parent interface{}) error {
 			}
 		}
 
-		// skip the table & scope, since they should be all setup by caller
-		return db.Create(source).Error
+		return tx.Create(source).Error
 	})
 }